Mechanical Alignment Versus Kinematic Alignment Total Knee Arthroplasty

Overview

Historically, total knee arthroplasty (TKA) has been performed with the goal of restoring a neutral mechanical axis, eliminating the average 3 degrees of valgus and varus of the distal femur and proximal tibia joint lines respectively. This is thought to provide a more stable and neutral joint-bearing surface. Because of this shift to a 0-degree knee angle, soft tissue releases are frequently required to balance the knee after making the distal tibia and proximal tibia cuts. More recently and increasingly, TKAs have been performed with a goal of restoring kinematic, or anatomic, alignment of the knee. This is thought to provide a more normal native knee angle, with the hopes of precluding the necessity of soft tissue releases to balance the knee. While some studies are promising regarding kinematically aligned TKAs (KA-TKA), at present, it is unclear how these compare to mechanically aligned TKAs (MA-TKA) in terms of patient reported outcome measures (PROM) when compared head-to-head. This study will randomize patients to receive either cemented MA-TKA or KA-TKA with the goal of assessing pain scores and PROMs at various time points following surgery.

Participants include patients 18 years or older presenting to the the investigators' institutions indicated for a primary total knee arthroplasty. Exclusion criteria include revision TKA, patients with prior injuries to study knee, patients with history of childhood knee disease, patients who cannot complete questionnaires in English, patients with comorbidities preventing surgery, and patients who are not able to provide informed consent. If, after examination, the patient is still eligible, the surgeon will introduce the study. If the patient is receptive, a member of the study team will approach the prospective patient to explain the study in detail. The study team members will emphasize the voluntary nature of participation and the prospective participant will be encouraged to ask questions and speak to others about participation. Once questions are answered to the prospective participant's satisfaction, they will be presented with the informed consent document (ICD). The study team member will exit the exam room to allow the prospective participant to carefully read the consent form. If they wish, prospective participants will be provided with a paper copy of the ICD to read and discuss with whomever they wish. Once the study team member and surgeon, if required, have answered any additional questions, the participant will sign the ICD. Preferably, the ICD will be signed in clinic. If a prospective participant has taken then ICD with them to consider or discuss with others, a study team member will plan a time to meet the prospective participant in the Orthopaedic Surgery clinic (likely in the preoperative holding area) to sign the ICD and complete the baseline questionnaires and ROM. Patients will have up until the day of surgery to decide if they would like to participate in the study. Informed consent will be obtained from participants before surgery. Preferably, the ICD will be signed in clinic. If a prospective participant has taken then ICD with them to consider or discuss with others, a study team member will plan a time to meet the prospective participant in the Orthopaedic Surgery clinic (likely when they return for preoperative clearance) to sign the ICD and complete the baseline questionnaires and ROM. Shortly after the ICD is signed, the participant will be randomized to either receive MA-TKA or KA-TKA. The participant will be blinded to the assignment until one year after surgery. The study team and surgeon will not be blinded to the assignment. Randomization will occur using stratified randomization lists per site. The Biostatistics Core at the Loyola University Clinical Research Office will provide randomization lists for each site to ensure equal 1:1 allocation of the two methods within each institution. Loyola Biostatistics will ensure randomization lists are readily available via REDCap at the time of consent/randomization. A member of the study team will communicate the randomization assignment to the surgeon and/or surgery scheduler. Preoperative instruction, surgery, and postoperative care/instructions will be the same for study participants as for patients who are not participating in the study. Two weeks after surgery, participants will return to the clinic for standard of care postoperative examination. The participant will be asked to complete questionnaires using a Loyola-managed electronic device. If desired, the participant can also request that a link to the questionnaires be emailed ahead of their appointment to be completed on their own device. Participants will also be asked to complete the same questionnaires prior to or at their standard 6-week postoperative visit and at the standard of care 1-year postoperative visit. All patients indicated for primary total knee arthroplasty will receive a cruciate-retaining cemented or cementless implant system, utilizing either MA or KA methodology. Both TKA types have been proven successful clinically and in the literature. A placebo would not be appropriate or ethical. Participants will be blinded to the assignment until one year after surgery. The study team and surgeon will not be blinded to the assignment. The primary aim of the study will be measured by the Patient Reported Outcomes Measurement Information System (PROMIS) Physical Function and Pain Interference item banks, the Knee Injury and Osteoarthritis Outcome Score (KOOS) Jr., the Forgotten Joint Score, and a validated 0-10 visual analog scale (VAS) of patient pain. KOOS Jr scores at 6 weeks post operation will be considered the primary endpoint. Secondary aims include evaluating KOOS Jr at 2 weeks and 1 year postoperatively. In addition to KOOS Jr, postoperative opioid consumption, pain scores, self-reported outcomes, range of motion, and survivorship will be collected at all time points. A 10-point difference in KOOS score is deemed clinically relevant between KA-TKA and MA-TKA methods. Using previously published data, KOOS has a conservative standard deviation estimate of 18. Using an independent sample t-test with 80% power and a 2-sided alpha value of 0.05, a sample size of 48 independent patients per method is sufficient to test the null hypothesis of no difference in KOOS, with an alternative hypothesis of +/- 10 points difference. With possible attrition of 5%, this sample size is inflated to 51 per group. The investigators' hypothesis is that patients with KA-TKAs will have higher PROMs compared to patients who receive MA-TKAs. MA-TKAs and KA-TKAs are commonly used procedures. Both procedures will be performed in a standard of care manner. There is no additional surgery risk to participants when participating in this study. Subject safety will be monitored like any other patient receiving a total knee arthroplasty by post-operative visits, patient-reported outcome measures, radiographic studies, and access to a contact number should patients have questions/concerns. Patients may experience a loss of confidentiality because of study participation. The frequency of this risk is rare. We do not expect any increased failure rate in either group as many studies have shown both techniques to be safe and efficacious. However, if there is a dramatic difference in failure rate our outcomes, we will halt the study.